1. Field of the Invention
The present invention relates to computer graphics and imaging processing systems, and in particular to an apparatus and method for producing rapid, high resolution hard color copies from computer-based graphics and digital image processing systems.
2. The Prior Art
There are many applications where it would be highly useful to provide rapid, high resolution hard color copies from computer-based graphics and image processing systems. Illustrations of such applications include management information systems, architectural rendering, non-destructive testing, medical imaging, electronic news gathering and the like.
One known prior art attempt to produce hard color copies from computer-based graphics and image processing involves a method where the composite color video image appearing on the screen of a monitor is simply photographed. This method has several inherent difficulties. For example, presently the broadcast standards in the United States require a sychronizing frequency and bandwidth standard that corresponds to a sequence standard of 60 hertz. This frequency limitation inherently limits the color spectrum that may be transmitted with such a signal, resulting in poor color definition (i.e. color hue, saturation and lightness) in the photographic reproductions taken from video images produced from such signals.
Moreover, the screen of a television monitor is electronically scanned 60 times every second. The area covered by a complete scan is referred to as a raster. Normally, each raster consists of 2621/2 scan lines covered in a one-field scan. A video frame or "page" consists of two 2621/2 line fields, or 525 scan lines which produce the composite video image. The sensitivity of most films is such that color copies of a composite video image have a poor resolution because of the chopping effect which results from the scan lines.
Another prior art approach to producing hard color copies from computer-based graphics has been developed by General Electric Company and is called the Genographics System. This system uses a substantially higher number of scan lines in order to improve the resolution of the copies. Although effective, this system is extremely expensive, which substantially reduces the applications where the system can be cost justified.
Accordingly, what is needed is an apparatus and method for producing hard color copies from computer-based graphics and digital image processing systems which is inexpensive, easy to use and which will reliably produce high resolution copies.